1. Technical Field
The present invention relates to an image display device.
2. Related Art
For example, an image display device that displays an image by scanning with laser light in a main scanning direction (a horizontal direction) and a sub scanning direction (a vertical direction) while intensity of the laser light is modulated has been known (e.g. JP-A-2003-287802).
As such an image display device, one displaying a full color image has been proposed as disclosed in JP-A-2003-287802.
A full color image is displayed by color development of three primary colors, i.e. red, blue, and green. However, in JP-A-2003-287802, laser light beams in two colors among the three primary colors are respectively irradiated on a screen so as to develop the two colors on the screen by diffusion of each color. In addition, by irradiating a laser light beam in an ultraviolet color onto a fluorescent substance that is evenly applied on the screen, the fluorescent substance is excited to develop the other color among the three primary colors.
A full color image is displayed by using a fluorescent substance as the above, enabling downsizing of a light source to be used, and further downsizing of an image display device and the like.
However, in the image display device according to JP-A-2003-287802, in a case where a thickness of a fluorescent substance on a screen is made thin, most of laser light beams in an ultraviolet color or a blue-violet color that are used as excitation light transmit through the screen without contributing to excitation of the fluorescent substance. As a result, not only an output of the excitation light laser is wasted, but also a light emitting amount of a fluorescent substance is reduced, and an unintended color change occurs to an image to be displayed. On the other hand, in a case where the thickness of the fluorescent substance on the screen is made thick, laser light beams in two colors other than the excitation light are diffused by the fluorescent substance and deteriorated, making use efficiency of the laser light beams in two colors unfavorable. Therefore, issues such as leading to deterioration of image quality in contrast, brightness and the like, and not sufficiently achieving a low cost and downsizing due to a need of a light source with high intensity arise.